Sexual Reversal with 17α-Methyltestosterone in Oreochromis sp.: Comparison between Recirculation Aquaculture System (RAS) and Biofloc Technology (BFT)

Precocity in tilapia implies the use of several methods of obtaining monosex seed; the most common tends to use masculinizing hormone 17α-methyltestosterone (17αMT), with variable results. Thus the objective of this study was to compare the efficiency of the sexual reversion process using 17αMT, in a recirculation system and in biofloc. In a totally randomized design, three tanks for recirculation (T-RAS) and three tanks for biofloc (T-BIO) with a capacity of 200 L effective volume were taken and filled with 1,056 larvae of Oreochromis sp., without reversing and with an initial weight of 0.02 g and an initial total length of 1.4 mm. The study was carried out during 65 d, the fish were fed (10% biomass, adjusted every 15 d) by a commercial diet at 45% of crude protein that included 17αMT (60 mg/kg). Water quality, microbiology, zootechnical and gonadal analysis were monitored. Consequently the water quality results showed that just dissolved oxygen (DO), temperature (T-°C) and alkalinity did not show significant differences. Additionally, in the productive parameters there were significant differences in the final length, the gain in length and in K which were better in T-BIO. The microbiological ones did not present significant differences between the treatments. Lastly, the percentage of reversion was significantly better in T-RAS. Then, this study suggests that settleable solids concentrations above 35 cm decrease the efficiency of the sexual reversion for this species.